Micro 6502 Journal Issue 2

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TTIMIl 6502 JOOJI^IM^IL

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NO a [L)^^ ^^^^^la 9^ $r50

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DECEMBER 1977/JANUARY 1978
ISSUE NUMBER TWO

Making Music with the KIM-1 3

by Armand L. Camus - How to write music for a DAC, with the complete
score for "Deck the Halls with Boughs of Holly"

Writing for MICRO - A Brief Note 7

Mixing Apples and Oranges - An Editorial 8

Meet the PET 9

by Charles Floto - An owner's view of the PET 2001

Digital-Analog and Analog-Digital Conversion Using the KIM-1 11
by Marvin L. DeJong - Experiments with a KIM-1 controlled DAC/ADC

MICRO Reviews: The First Book of KIM 14

The PET Vs. the TRS-80 17

by Bob Wallace - A feature-by-feature comparison

Ludwig von Apple II 19

by Marc Schwartz - How to write music for the APPLE II

MICROBES - Tiny Bugs in Previous MICRO 22

The Challenge of the OSI Challenger 23

by Joel Henkel - An owner's impressions of the OSI Challenger

Improving Keyboard Reliability 25

by MOS Technology - A hardware modification for your KIM-1

Important Addresses of KIM-1 and Monitor 27

by William Dial - A Programmer's Reference Card for the KIM-1

CGRS Microtech

The COMPUTERIST

Computer Playground

Computer Shop

the enclosures group

Advertisers Index

8 F&D Associates 22

2 JADE CO 20,21

16 MICRO Subscription Form 25

26 Pyramid Data Systems 8

IFC Riverside Electronics 22

Subscription Rate: $6.00 per year (six issues) in U.S.A.

MICRO is published bimonthly by The COMPUTERIST, 8 Fourth Lane
So. Chelmsford, MA 01824. Robert M. Tripp, Editor/Publisher.
Controlled circulation postage paid at Chelmsford, Massachusetts.

Copyright 1977 by The COMPUTERIST. All Rights Reserved.

Deadline for February/March 1978 issue: January 15, 1978.

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2:1

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Making Music with the KIM-1

Armand L. Camus

P.O. Box 294

Westford, MA 01886

What kind of music can you make with the help
of a microcomputer, namely the KIM-1 with its
I.IK bytes of memory? Well, it certainly will
not sound like the Boston Symphony Orchestra,
live or on records, but with the right type of
music it will give an acceptable rendition of a
chosen piece of music. Many elements of good
music will be missing, especially the timbre of
the different instruments of the orchestra, but
on the positive side the notes will be on tune,
you will be able to compose in four-part har-
mony, the tempo will be adjustable, and the
whole process will permit some of the artistic
creativity which may hide in each of us to
emerge to the surface. Last, but not least, it will
be a lot of fun.

This elementary article explains the "HOW-TO"
rather than the "WHY" in making music with a
microcomputer. Many of the hobbyists who
may find it too simple may refer to the excellent
article by Hal Chamberlin which dwells in detail
on the subject.

An easy way for the beginner to start his
musical career is to acquire a minimum of
equipment besides the KIM-1 and cassette re-
corder it is assumed are already in his posses-
sion.

The DAC unit is a printed circuit board con-
taining a complete audio output system for the
KIM-1. This board also comes with a cassette
tape, an instruction sheet listing the songs which
can be loaded in the KIM, and a reprint of the
reference article including the interconnections
to be made between the two connectors.

Now that we have described the hardware we
will concentrate on what to do in order to get
some music out of the system. The simplest way
at this time is to load File 1 and File 2 of the
tape and to see if the Star Spangled Banner
comes out clear and patriotic. The procedure is
simple:

J KIMA

□D

Con>men>

Jl, J2 connectors: Vector R644, Winchester
HKD2250, or equivalent. J2 will be too long,
but will work just the same.

Speaker, 2^/2", 8 ohm, 0.3W, from Radio Shack,
or equivalent.

DAC Digital-to-analog converter from THE
COMPUTERIST, P.O. Box 3, S. Chelmsford,
MA 01824 or MTU, P.O. Box 4596, Manchester,
NH 03103.

^

2:3

l^3(S^(Dl

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start the KIM-1
keys to get:

and press the appropriate

AD OOFl DA 00
AD 17F9 DA 01
AD 1873 Press -GO

Start the cassette until you get 0000 in the
address display, which indicates that the load-
ing was done properly. After stopping the
cassette, press the keys to get:

AD 17F9 DA 02
AD 1873 Press GO

Start the cassette again until you get 0000.
Stop the cassette. Now you are ready. Press
AD 0100, press GO and the song will be
played. As it stops, the program resets the
address AD to 0100, so by pressing GO again,
the song will repeat itself.

In the same manner you could load Files 3 and 4
to get a rendition of Exodus. The sound quality
may be changed by loading File 5 or File 6. Per-
sonally, I prefer File 6 which has a much
more mellow timbre.

Transcribing A Song

Now that we have gone through the above
steps, we will learn to code a song. For our
purpose, a particular note of music will have
two characteristic elements:

its pitch, represented by its position on the

staff

its duration, relative to other notes.

What we mean is that a half note lasts twice as
long as a quarter note, a quarter note lasts twice
as long as an eighth note, etc. . . We are not talk-
ing about tempo yet, this will come later.

1. Duration Code:

We will assign a two-digit code to the
duration of a note:

o = FF d=80 J-=60 J
J.=30 J*=20 J^=IO

= 40

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2. Pitch Code

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Norm c 5 55 P flt G"
COOe 6Z 60 SK SC SR Se

Gfc F E E£> p pb C
5*6 rtf 52. 50 A.E f|.C h-ti

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08 06 04- 02.

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With the help of this lookup table we can find
quickly the code for any note within the limits
of C6 and C2, the high and low C's. However,
the very low notes may not be reproduced too
well with a small speaker and it may not be ad-
visable to go below C3 (Code lA).

3. Coding A Song:

The program given at the end of this article is a
coding of the well-known carol "Deck The Halls",
which we thought would be appropriate for this
issue. [Editor's Note: It inspired this issue's
cover!] If you look at this coding, you will
observe that it is done line by line. Each line is
composed of six elements. For example, the
first line is :

0200 60 4A 44 32 24

- the 0200 is the memory address of the
element 60. The next element, 4A, would
then have an address 0201, and so on.

- the 60 is the duration of the group of four
notes which follow. A 60 means a dotted
quarter note.

- the 4A is the note C, for the first voice.

- the 44 is the note A, for the second voice.

- the 32 is the note C, for the third voice.

- the 24 is the note F, for the fourth voice.

This is an F major chord which could be re-
presented as in (1), and it corresponds to the
word "DECK" of the song.

Now we will code the first bar of the song.
Remember that each line will have the same
format:

address (4 digits), duration (2 digits), 1st
voice (2 digits), 2nd voice (2 digits), 3rd
voice (2 digits), £ind 4th voice (2 digits) for
a total of fourteen (14) digits. If a voice is
quiet, use 00 at the appropriate location.

The first vertical group of notes (C,A,C,F)
corresponding to the word "DECK" has al-
ready been explained above.

The second vertical group of notes correspond-
ing to the word "THE" is made of B flat, G, C,
and E. Looking up the pitch code table, we find
the following codes:

Bb = 46, G = 40, C = 32, and E = 22. Each
note is an eighth note so the duration code is
20. The address of the duration code is 0205
so our second line will be:

0205 20 46 40 32 22

In the same fashion the two other vertical groups
are made of quarter notes (code 40) and we get
for the first bar:

0200 60 4A 44 32 24 (DECK)
0205 20 46 40 32 22 (THE)
020A 40 44 3C 32 24 (HALLS)
020F 40 40 3A 2E lA (WITH)

oecK

QCCK TM6 HALLS WiTH

U- ^ ^ J

y, r- IT r ^

J. J.-J J

^ T T r

Remember that there is a Key Signature in this
carol and that all the B's, wherever located on
the staff, are flat, unless otherwise indicated,
which explains the 46 of the second line and the
2E of the fourth line.

Another part of that song is shown in the ex-
ample (3). The first voice plays two notes (A
and B natural), while the other voices play
only one. We solve this problem by writing two

lines, one for the A and one for the B natural,
repeating the other notes to extend their dura-
tion to a quarter note. We get:

02D2 20 44 3C 32 24
02D7 20 48 aC 32 24

Both A note (code 44) and B natural note
(code 48) have only the duration of one eighth
note each (code 20), and we have to write two

^

2:5

separate lines for them, but the three other
notes will be repeated so that their total dura-
tion is a quarter note. Fortunately, the lower
notes, even when repeated, will blend together
and sound more like a quarter note than two
consecutive eighth notes.

Now we should be able to code a song, but as a
preliminary exercise, you may want to load
"Deck the Halls" and see how it works out. Here
is the procedure :

Load Files 01 and 02 of the DAC tape, as ex-
plained at the beginning of this article. You may
also want to load File 06 to give a more mellow
timbre. Then go to address 0200 and start in-
putting the data. The addresses in the left side
give you a check on your progress and catch
possible omissions of data. What we are doing
here is using the main program and writing over
the song already in memory. At any time it is
possible to go back to AD 0100, push GO and
listen to what is already in memory. Somewhere
at about 2/3 of the song, we run out of memory
(0200 to 02F9), but we have enough left to tell
our microcomputer that it is the end of that
particular segment (02FA 01), and that we wish
to continue at address 0083 (02FB and 02FC).
At the very end, check address OODD 00. The
data 00 indicates the end of the piece and this
will reset the KIM-1 to address 0100, ready to
"GO", so to speak.

After you have loaded the code and pushed the
GO key, the carol should start, sounding good if
no mistake was made, but perhaps a little bit
on the slow side. To change the tempo, either
way, go to address OQID and the data will pro-
bably show 60. Change the data to 40, go back
to address 0100, push GO and the tempo will be
much faster. Experiment with the data at AD
OOID and find the tempo you prefer.

I have found out that while I am coding I like to
listen to what is already in memory, because a
simple mistake at the beginning, especially for-
getting one voice or the duration code, will

throw the rest out of whack. Starting the song
at the beginning, when it is already correct is
a waste of time, but it is possible to start the
song at some other point. However, it must
always be at one of the duration addresses
shown at the end of this article. If not, the
KIM-1 would interpret the duration code as a
musical note and vice-versa! The starting ad-
dress is contained in locations 0017 and 0018.
To start, for example, at address 0237, go to
address 0017 read 00, 0018 read 02. This means
that the song normally starts at 0200. All we
have to do is change the data to read :

AD 0017 DA 37
AD 0018 DA 02

Then setting address 0100 and pushing GO will
cause the song to start at location 0237 every-
time.

Available Memory

The memory available to the user is divided in
two groups, each group not necessarily in con-
secutive order. First group is associated with the
music program, frequency table or the notes,
KIM, etc. . . Second group is associated with the
song. The actual layout of the memory is as
follows:

Program variables
Note frequency table
Song, second part
KIM variables
Music program
Song, third part
6502 Stack
Song, first part
Waveform (voice) table
Song, fourth part

If your music score extends beyond the first
part locations, you have to provide room for
continuation. Assuming a score uses all of the
available memory space for coding a song, the
following locations are important:

0000 to

OOIE

001 F to

0082

0083 to

OOEE

OOEF to

OOFF

0100 to

OlAA

01 AB to

01 F3

01 F4 to

01 FF

0200 to

02FF

0300 to

03FF

1780 to

17E4

Use of Location

Parti

Part 2

Part 3

Part 4

Beginning of Part (Song)
Beginning of Last Line
Last note of Last Line
End of Sequence (Song)
Low Address Next Segment
High Address Next Segment

Reference: Chamberlin, Hal, "A Sampling of Techniques for Computer Perform-
ance of Music", BYTE Magazine, Sept. 1977, pp. 62-83.

0200

0083

OlAB

1780

02F5

00E7

OlEC

17DF

02F9

OOEB

OlFO

17E3

02FA(01)

OOEC (01)

OlFl (01)

17E4 (00)

02FB(83)

OOED (AB)

01F2 (80)

02FC (00)

OOEE (01)

01F3(17)

^

2:6

0200:
0205:
020A:
020F:
02U:
0219:
021E:
0223:
2 2 8:
022D:
0232:
0237:
023C:
0241 :
0246:
024B:
0250:
0255:
025A:
025F:
0264:
0269:
026E:

0273:
0278:
027D:
0282:
0287 :
028C:
0291 :
0296:
029B:
02A0:
02A5:
02AA:
02AF:
02B4:

60
20
40
40
40
40
40
40
20
20
20
20
60
20
40
40
80
60
20
40
40
40
40
40
40
20
20
20
20
60
20
40
40
80
60
20
40

4A

k^i

44

40

3C

40

44

3C

40

44

46

40

44

40

3C

3A

3C

62

5E

5C

58

54

58

5C

54

58

5C

5E

58

5C

58

54

52

54

40

44

46

4^
40
3C
3A
32
3A
3C
32
3A
3C
40
3A
3C
36
32
32
32
5C
58
54
52
4E
52
54
4A
52
54
58
52
54
4E
4A
4A
4A
3A
3C
40

I
3X
3V
32
2E
2C
32
32
2C
32
32
32
32
32
2E
2C
28
2C
32
32
32
2E
2C
32
32
2C
32
32
32
32
32
2E
2C
28
2C
32
32
32

52
22
24
1A
IE
1A
24
24
1A
1A
1A
1A
24
16
1A
1A
24
24
22
24
1A
IE
1A
24
24
1A
1A
1A
1A
24
16
1A
1A
24
1A
1A
1A

Score for "Deck the HaUs"

02B9
02BE

02C3
02C8
02CD
02D2
02D7
02DC
02E1
02E6
02EB
02F0
02F5
02FA
02FB
02FC

0083
0088
008D
0092
0097
009C
00A1
00A6
OOAB
OOBO
00B5
OOBA
OOBF
00C4
00C9
OOCE
00D3
00D8
OODD

Writing for MICRO

MICRO is interested in all aspects of microcomputers based on the 6502 micro-
processor family. Our primary coverage is aimed at factual, useful information.
This may be "How To" articles, useful programs and subroutines, descriptions of
working applications, special interest groups such as Hams, reviews of products
and literature, technical tutorials, and so forth. Authors will receive a small
honorium plus reprints of their article. Help spread the 6502 word.

^

2:7

^v

Mixing Apples and Oranges

An Editorial

Often you have heard the injunction against mixing apples and oranges. MICRO
proposes that we ignore the warning and mix APPLEs (I and II) with PETs, KIMs,
Challengers, CGRS Microtechs, JOLTs, homebrews, and any other 6502 family based
microcomputers. The hope is that mixing these devices together will help to
show the similarities between them that are inherent by reason of their common
microprocessor. This is the passive role of MICRO. The active role of MICRO is
to promote commonality among these microcomputers. How about establishing a
standard assembler syntax (since the MOS Technology syntax is so horrible)?
How about defining some standard subroutines and subroutine calling sequences
so that it will be easier to adapt programs from one machine to run on another?
Would it be possible to develop some standard cassette tape format which would
permit tapes generated by one microcomputer to be read into another? Wouldn't
it be nice if the 6502 based BASICs, Disk Operating Systems, and other high
level software was compatible across machines? Maybe it is only a dream, but
maybe it isn't too late to seriously attempt to maximize the impact of the 6502
based systems by setting some standards so that the various 6502 systems can
combine to strengthen our position in the micro world rather than weaken it by
producing incompatible hardware and software. 6502 interests of the world unite!
You have nothing to lose.

^

2:8

FINALLY I

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^B 8100 8TANOARO BUB COMPATIBLE

^ MPU CARD WITH BK RAM-aKROM ONBOAnO

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^m O.M.A. FRONT CONTROL PANEL

• INTROOUCTORV SYSTEM

MPU CARO : IK RAM
FRONT PANEL : HEX DISPLAY

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T.I.M. I/O CARD

SIOO MOTHERBOARD : 7 SLOT
POWER SUPPLY BV:iaA
t1SV:1A

SEND CHECK OR MONEY ORDER TO:
CORS MICROTECH
P.O. BOX 3SS
SOUTHAMPTON , PA

^

Meet the PET

Charles Floto

267 Willow Street

New Haven, CT 06511

Copyright 1977 by Charles Floto

This article is based on about a month's experi-
ence with PET model 2001-8 serial #0010081.
Commodore indicates the only thing experi-
mental about it is the color of the case, which is
metal painted white.

In June I sent Commodore $595 for a PET with
4K of RAM to be delivered in late September.
Toward the end of the latter month I was in-
formed that initial production would be limited
to the 8K version and that I could either send an
additional $200 or get my money back. I sent
the $200 and my PET was delivered October 25.

It made the trip from Palo Alto to New Haven
well cushioned in a carton 21" x 23" x 19"
high. Since being unpacked my PET's survived
riding on a bus seat to Washington, D.C. and
returning by car.

While the case has a maximum width of I7V2"
and a maximum depth of 19" the placement of
the feet allows it to stand on anything at least a
foot square. Maximum height is IbW and the
PET weighs about 37 pounds.

A glance at the PET reveals its distinguishing
characteristic: everything's in one package --
including video display, keyboard, and tape
drive. A standard 9" diagonal black and white
TV tube is used. The display field measures
about 4%" high by 6" wide. This is divided into
25 lines of 40 columns. Each of these 1000
positions can be filled with one of about 300

different characters formed with an 8 x 8
matrix. Character width is about % of character
height. Characters available include those shown
on the drawing of the keyboard. Any of these
may also be displayed with black and white
reversed on an individual basis. Furthermore, by
changing the contents of memory location
59468 you can substitute lower case letters and
four additional graphics for 30 of the graphics
characters. Taking video inversion into account,
this gives a total of 316 available characters.

The graphics characters have been chosen to be
useful picture elements which give higher effect-
ive resolution than the 25 x 40 field would
suggest. For example, a horizontal bar graph can
be displayed with resolution better than 1/3 per
cent of full scale.

Characters may be placed on the screen directly
from the keyboard, by use of the PRINT com-
mand, or by a POKE into the screen memory.
This extends from decimal address 32768 to
33767 (i.e., 32K to 32K + 999). If A is a number
in this range and C is between and 255 then
POKE A, C will place a character on the screen.

The keyboard is the PET's most controversial
feature. It takes up an area 9" by 2%". Since
I'm used to typing with only two fingers and a
thumb the small size and rectangular layout
don't bother me. Each keytop is about 3/8"
square and can be depressed about 1/8". The
feel is similar to a standard spring-loaded switch-

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^

2:9

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closure keyboard. The only trouble I've had
with it is that occasionally one of the cursor
control keys will insert a character rather than
move the cursor. IVe been able to rectify this
by getting off the line and then coming back to
it. Preliminary investigation suggests it should
be quite easy to attach a standard keyboard to
the PET.

The other prominent external feature of the
PET is the tape drive which takes up an area
just over 5" square. It has the useful function
controls, but the motor is turned on and off
under software control in the play and record
modes. Prompts for operation of the controls
are displayed on the screen as appropriate. The
screen also displays status of the tape operation
in progress. When attempting to load or verify
a fUe with a specified name it displays the names
of other files found. File names may have a
maximum of 79 characters.

Short BASIC programs can be loaded from tape
at an effective speed of 250-400 baud, with
longer programs having a higher net rate. It
should be possible to fill the entire 8K of RAM
in under 2^/2 minutes -- once the proper program
has been found.

Sticking out of the lower right side of the PET
cabinet is a 40 line (plus 40 ground) printed
circuit connection to the internal bus. As it
does stick out about 1/8" metallic objects
should be kept away from this area. The three
groups of PC connectors in the rear present a
lesser hazard as they're flush with the cabinet.
These are: 1. A connector for the IEEE-488
bus (see MICRO No. One, page 11 for my
discussion of this); 2. A parallel port with hand-
shaking; 3. The interface for tape drive #2.
I was able to verify this one by removing drive
#1 from the cabinet and plugging it into the
rear as #2. Commodore has exhibited the PET
with a second drive connected, but hasn't
offered to sell any yet.

So much for physical externals. How good is the
firmware stored in that 14K of ROM? Since my
instruction book hasn't arrived yet I'll limit my
comments to the 8K BASIC interpreter describ-
ed in the nine-page "temporary version" of the
documentation.

My favorite feature of PET BASIC is the ease of
editing a line within a program. Just move the
cursor to the appropriate spot, make the change,
and hit RETURN - no need to retype the line.
It's also handy to be able to turn on the machine,
load a partially-written program from tape,
work on it for a while, then save the new version
on cassette, I'm glad I got the version with 8K
of RAM as I've already written a program that
leaves fewer than 5K bytes free. (The 4K model
is said to use a different circuit card, but since
there aren't any yet. . . )

I also appreciate the special variables TI and
TI$. TI is incremented 60 times a second; it
makes delays and timing applications easy.
TI$ is a 24-hour clock whose 6 digits indicate
hours, minutes, and seconds. As these suggest,
variable names may be two letters ~ as long as
they're not reserved words such as OR, IF and
ON. Variables may be integers, strings, real, or
multi-dimensioned arrays of any one of these.
Integers are limited to the range ±32767. Real
variables are calculated with 10-digit precision,
although only 9 digits are printed. For example,
pi=3.14159265; twice pi=6.28318531.

Another distinctive feature is the GET state-
ment which reads the keyboard without RE-
TURN having been pressed. Unfortunately
the random number function only works with
positive arguments. RND(0)=.564705882 always,
whUe RND(-l)=2.99196472E-08. The latter is
typical of the values returned with negative
integer arguments. This is the only bug I've
discovered in PET BASIC.

Editor's Notes: In MICRO #1, Charles Floto discussed the PET's IEEE-488 Bus.
Since then Motorola and Intel have both announced new ICs that will make it
easy to interface to this otherwise formidable bus structure. For more
information on the PET and a comparison with the Radio Shack TRS-80, see
"The PET Vs. the TRS-80" by Bob Wallace, MICRO #2, page 17.

^

2: 10

i>

Digital-Analog and Analog-Digital Conversion
Using the KIM-1

Marvin L. De Jong

Department of Math-Physics

The School of the Ozarks

Point Lookout, MO 65726

A Motorola 1408 8-bit digital to analog conver-
ter is connected as shown in the circuit diagram.
(The 1408 is available from James Electronics,
1021 Howard Ave., San Carlos, CA 94070, as
are the op amps used in these experiments.)
The PAD port of the KIM is used to provide the
digital input to the 1408. The analog output of

Circuit Diagram for
Digital to Analog Converter

the 1408 is a current sink at pin 4, which we
converted to a voltage by means of the RCA
CA3140 operational amplifier. The feedback
resistor R is adjusted to give the desired voltage
output. For example, an R of about 500 ohms
gives a voltage range from volts when PAD is
00000000 to 1 volt when PAD is 11111111.

PB<^-

SCOPE smc
■xo Scope

*ISV

*PB7

1 . Generation of a Ramp Voltage Waveform

For the first experiment do not connect the
second op amp, simply connect the output of

the first op amp to an oscilloscope as shown.
Load the following program.

Program to Generate a Ramp Voltage Waveform

ADDRESS

OPCODE

LABEL

INSTRUCTION

COMMENTS

0300

A9 FF

START

LDAIM FF

255 in Accumulator

0302

8D 01 17

STA PADD

Port A is Output Port

0305

EE 00 17

BACK

INC PAD

Increment number in PAD

0308

4C 04 03

JMP BACK

Increment in a Loop

Running this program should cause a ramp wave-
form to be observed on the oscilloscope screen.
A close examination of the ramp will show that

it consists of 2* = 256 steps rather than a
straight line.

^

2:11

iN

2. A DAC as an Analog to Digital Converter

The second op amp acts as a comparator. It
compares the voltage from the output of the
first op amp (which we shall call the digital
signal) with a voltage from some source to be
applied to pin 3 (which we shall call the analog
signal). The output is connected to PB7 on the
KIM. If PB7 = 1, the analog signal is greater
than the digital signal. If PB7 = 0, the analog
signal is less than the digital signal. The digital
signal is, of course, produced by the contents
of PAD.

A flow ch£irt showing what we intend to do is
shown below. Output port PAD is set to zero. If
the analog signal is positive the PB7 = 1 . PAD is
now incremented until the comparator indicates
that the analog signal is less than the digital
signal, i.e. PB7 = 0. At that instant the digital
and analog signals are the same to within one
bit, the least significant bit, on PAD. The
digital value of PAD is then displayed and the
cycle continues.

If the feedback resistor is adjusted so that a
value of PAD = 255io = FFl6 produces a volt-
age of 2.55 volts, then we have constructed a
simple digital voltmeter with a full scale reading
(in hex) of 2.55 volts. The extremely high im-
pedance of the 3140 op amp makes this a rather

good voltmeter. A simple program to convert
from hex to base ten would make the meter
easier to read.

Flow Chart for
Analog to Digital Converter

AD = PAD+1

1

DISPLAY PAD
CONTENTS ON
KIM

Program for Analog to Digital Converter
(Ramp Approximation)

ADDRESS OPCODE

LABEL INSTRUCTION COMMENTS

0300

A9 FF

START

LDAIM

FF

0302

8D 01 17

STA

PADD

0305

A2 00

AGN

LDXIM

00

0307

BE 00 17

RAMP

STX

PAD

030A

AD 02 17

LDA

PBD

030D

10 O^i

BPL

DISP

030F

E8

INX

0310

^C 07 03

JMP

RAMP

0313

86 F9

DISP

STX

INH

0315

20 IF IF

JSR

SCANDS

0318

He 05 03

JMP

AGN

255 in Accumulator

Make Port A Output Port

Start PAD at zero

Output Value of X register

Read Port B

Branch if bit 7 =

Increment X register

Continue loop

Put X into Display register

Use KIM Display Subroutine

and start again at zero

^

2: 12

Successive Approximation Analog to Digital
Used as a Storage Scope.

^W

The ramp approximation is quite slow and there
is a faster technique known as "successive ap-
proximation." It works as follows: the most
significant bit to the DAC is set to one and all
the others are set to zero. If the comparator in-
dicates that the analog signal is greater than
the digital signal, the next lower bit is set to 1
and the test is repeated. If the comparator in-
dicates that the analog signal is less than the
digital signal, the highest bit is made zero, and
the next lower bit is set to 1 and the test is re-
peated. This iterative process is repeated until all
eight bits have been tested, starting with the
MSB and ending with the LSB. The flow chart
indicates how this will be accomplished.

This analog to digital conversion scheme will be
used in a program which digitizes 256 points on
a waveform and then stores the results, to be
displayed at a convenient time and with as many
repetitions as desired on an oscilloscope. It is
useful for examining slow waveforms with an
oscilloscope with a low persistance screen, for
example ECG waveforms, and it is useful for
examining non-periodic waveforms such as a
one-shot impulse from an accelerometer. The
program has triggering built in, and the output
scan portion synchronizes the oscilloscope with
a sync signal, turning an inexpensive scope into
something more useful. A flow chart for the
program is given below.

Flow Chart for

Successive Approximation

Analog to Digital Conversion

Flow Chart for Storage Scope

\.

PAD = 80^g = 10000000
PGZZ = 80^g = 10000000

YES

PAD = PAD - PGZZ

LOGICAL SHIFT RIGHT PGZZ,
(Shifts all bits one bit
right and zero bit is
shifted into carry bit.)

I

PAD = PAD + PGZZ

^ET trigger)

^TART timer)

( DIGITIZE J

r GO TO >(
V DISPLAY J

2: 13

r^

SN

A short description of the behavior of the cir-
cuit and program follows. The experimenter
chooses the desired trigger level and loads this
into location 0306. When the analog signal is
greater than this, the comparator makes PB7 go
high and the scan begins. The sampling rate and
the scan time is determined by the number load-
ed into the timer and the timer used; locations
0314 and 0316, respectively. It takes at least
200 microseconds to digitize so there is no
point in choosing time intervals smaller than
this. X is used as an index to identify each of the
256 points on the sc£in. After the timer is
started the analog signal is digitized and the
timer is watched until it is finished. X is then in-
cremented and a new point is digitized until all
256 points are finished £ind stored in TABLE.X.

X is then zero again. This entire process will
repeat unless the 1 key is depressed, in which
case the program displays the data on the oscil-
loscope, connected as before to the output of
the first op amp. The display will repeat, com-
plete with SYNC signal output from PBO,
until the program is halted. In our case we load-
ed the vector 17FA and 17FB with the starting
address of the program (0300) so a depression
of the ST key caused the entire program to
start over.

A listing of the program is shown on the follow-
ing page. Notice that the data is stored in
TABLE,X located in page 2 of memory, PGZZ
is at location 0000, the trigger level is in 0306
and the scan time variable is in 0314 and 0316.
The scan time should not be shorter than 200
microseconds. As far as display is concerned, we
found that a sweep rate of 200 to 500 micro-
seconds per cm gave good results.

Flow Chart for Display

fesT X = ;

-<^

(sync scope)

PUT
TABLE (X)
INTO PAD

( X = X + 1 j

A few other comments may be in order. First,
most of the ideas for this project were obtained
in a KIM workshop offered by Dr. Robert
Tinker. The software implementation is the
author's work. There are some obvious improve-
ments, such as a sample and hold device between
the £inalog source and the comparator or a faster
approximation routine. These improvements are
left for the reader to implement. The author
would be glad to be informed if such improve-
ments are made.

^
/i

i£D3(3a(£)i

^v

MICRO Reviews:

The First Book of KIM

This is one terrific book for anyone who has a KIM-1. It was assembled by Eric
Rehnke (Publisher of "KIM-1 /6502 User Notes"), Jim Butterfield ("Hypertape" and
many other good utilities), and Stan Ockers (a regular "User Notes" contributor).
Over half of the book is devoted to "Recreational Programs", games you can play
on your basic KIM-1. The section on "Diagnostic & Utility Programs" is worth
the price of the book by itself. The remainder of the book contains tutorial
information on getting started with your KIM-1 , expanding your system, and inter-
facing to the outside world. This well produced, 176 page resource is available
for $9.50 (including postage in USA) from:

ORB

P.O. Box 311

Argonne, IL 60439

^

2: 14

^

Program for Storage Scope

ADDRESS OPCODE

LABEL INSTRUCTION COMMENTS

0300

A9

FF

BEGIN

LDAIM

FF

0302

8d

01

17

STA

PADD

0305

A9

10

START

LDAIM

TSET

0307

8D

00

17

STA

PAD

030A

A2

00

LDXIM

00

030C

EA

NOP

030D

EA

NOP

030E

AD

02

17

TRIG

LDA

PBD

0311

10

FB

BPL

TRIG

0313

A9

CO

STIME

LDAIM

CO

0315

8D

05

17

STA

TIMER

0318

A9

80

LDAIM

80

031A

85

00

STAZ

PGZZ

031C

8d

00

17

TEST

STA

PAD

031F

AC

02

17

LDY

PBD

0322

30

03

BMI

FWRD

0324

38

SEC

0325

E5

00

SBCZ

PGZZ

0327

46

00

FWRD

LSRZ

PGZZ

0329

BO

08

BCS

OUT

032B

65

00

ADC

PGZZ

032D

4C

1C

03

JMP

TEST

0330

8D

00

17

OUT

STA

PAD

0333

9D

00

02

STAX

TABLE

0336

E8

INX

0337

FO

08

BEQ

DISPLY

0339

AD

07

17

CHEK

LDA

TCHEK

033C

10

FB

BPL

CHEK

033E

4C

13

03

JMP

STIME

0341

20

6A

IF

DISPLY

JSR

GETKEY

0344

C9

01

CMPIM

01

0346

FO

03

BEQ

SYNC

0348

4C

05

03

JMP

START

034B

A9

01

SYNC

LDAIM

01

034D

8D

03

17

STA

PBDD

0350

A2

00

LDXIM

00

0352

AD

02

17

RPT

LDA

PBD

0355

49

01

EORIM

01

0357

8D

02

17

STA

PBD

035A

BD

00

02

SCAN

LDAX

TABLE

035D

8D

00

17

STA

PAD

0360

E8

INX

0361

DO

F7

BNE

SCAN

0363

4C

52

03

JMP

RPT

Initialize Port A to Output
TSET Trigger Voltage Set

Initialize X register

Tinput and test PB7

Wait if PB7 =

Set Scan Time here

Select Interval Timer

Start Digitize Sequence

Store Initial Value

Output Value

Test PB7

Branch if PB7 = 1

Clear Borrow Flag

Subtract bit 7

Set PGZZ for Next Lower Bit

Out of Digitize Loop if Finished

Set Next Lower Bit = 1

Return to Test all Lower Bits

Final Approximation in PAD

and in TABLE (X) in Page 2

Bump Table Index

Go to Display if Table Complete

Test if Timer is Finished

If not, Wait in Loop

Digitize another Point

Is Key 1 Depressed?

Yes. Display the Data
No. Return to Start
Set up PBO as Sync
Output Pin

Init X to Display Table
Toggle PBO for Sync
Signal to Scope

Output Table (X) for

Display on Scope

Increment X register

Continue until all Points Done

Then Repeat

NOTE: This material was submitted by the
author to the KIM-1 User Notes and has also
been distributed by MOS Technology as "KIM

Application Note #11701." It is printed here
with the permission of the KIM-1 User Notes
and MOS Technology.

^

2:15

COMPLETE, READY TO USE, APPLE II MICROCOMPUTER WITH BASIC AND SYSTEM MONITOR IN
ROM AND 16K BYTES OF RAM. Apple II with 8K of RAM $1391.75

Additional 8K Memory Expansion When Purchased With System $106.25

TOTAL 16K SYSTEM ONLY $1498.00 - SAVE $200

APPLE II PERIPHERAL INTERFACE CARDS:

■ S-100 BUS INTERFACE ($160)'''

- Connect the Apple II to an S-100 Bus Motherboard

- Will Run Almost All Memory, I/O, and Special
Purpose S-100 Boards

- All Interconnecting Cables and Plugs Supplied (S-100
Motherboard and Power Supply Not Included)

PROGRAMMABLE PRINTER INTERFACE ($80)

- Onboard EPROM Printer Driver

- Full Handshake Logic

- High Speed Parallel Output Port Capability

- Provision for 256 Byte I/O Drive in EPROM

- Printer, Driver Programs Available for Centronic,
SWTPC-40, and Other Printers

Delivery January, 1978.

FLOPPY DISC INTERFACE TO PERSCI ($80)

- Programs Saved and Loaded by Name

- Powerful Firmware DOS File Handling Capability

- Storage Capacity of 252K Bytes per Disc

- Up to 4 Drives (One Million Bytes)

- File Handling as Easy as Inputing or Printing

- Access Methods: Stream, Punctuated, Relative, Direct

APPLY POWER CONTROL INTERFACE''"

- Up to Sixteen Control Channels

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Systems, Electrical Appliances

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• Apple Power Interface Board and One Power
Control Module ($85)

• Additional Power Control Modules (Controls Four
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• Appliance Control Module (Controls One AC
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ADD ON MEMORY FOR APPLE II

SOFTWARE FOR APPLE II

■ Set of Eight 4K RAM CHIPS

$ 44

■ Home Financial Record Program (Req. 16K Sys)

$ 20

■ Set of Eight 16K RAM CHIPS

$540

■ Business Inventory (Req. 20K Sys)

$ 40

■ Upgrade of Apple II Memory Using Modified

■ Bob Bishop's High Resolution Games (Req. 16L Sys)

$ 40

4K RAM Memory Expansion

- Star Wars

$ 15

- 4K to 16K

$250 .

- Rocket Lander

$ 15

- 8K to 16K

$160

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$ 15

- 12Kto 16K

$ 80

■ Apple Music (Three Octaves)

$ 20

■ Data Save to Cassette

$ 20

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APPLE II CLASSES

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■ Introductory Basic (Three-Two Hour Classes) $ 20

■ 6502 Programming Manual

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■ 6502 Hardware Manual

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■ 6502 Assembly Language (Five-Two Hour Classes) $ 50

■ Apple 11 Low and High Resolution Graphics and

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Mastcrcharge, Visa. B of A accepted. No C.O.D. Allow two weeks for personal check to clear Add $1.50 for handling and postage. For
computer system, please add $10.00 for shipping, handling, and insurance. California residents add 6% sales tax.

^

The PET Vs. the TRS-80

Bob Wallace

P.O. Box 5415

Seattle, WA 98105

The $600 computer has arrived! The PET (Pro-
grammable Educational Terminal) by Commo-
dore, and the TRS-80 by Radio Shack, usher in
a new era of personal computing. Both are
assembled computers, with video display, key-
board, audio cassette storage, and BASIC; both
initially come with 4K bytes of user memory.
There the similarity ends; each has significant
advantages and disadvantages. I should mention
my bias at the outset; I'm for the PET. Some
cynical souls will think it's because the store
where I work can carry the PET and not the
TRS-80; however, the real reason is the PET's
much better BASIC. More on this later.

Let's start with the hardware, which I consider
about evenly balanced. The PET uses the 6502
microprocessor; as a matter of fact. Chuck
Peddle, who designed the 6502 for Mos Tech-
nology, also designed the PET. Clock speed is

1 Mhz so a "load immediate" instruction takes

2 microseconds. The TRS-80 uses the Z-80
microprocessor, with a 1.776 Mhz clock. This
gives a "load immediate" time of 3.94 micro-
seconds. In general, the Z-80 has a more advanc-
ed instruction set (both manufacturers should
have assemblers available in 1978). The actual
speed of the BASIC depends more on the
BASIC interpreter than the cycle times. If the
speed is important to you, wait for the inevi-
table published benchmarks.

As mentioned, both units come with 4K of
RAM; you can pay $200 more for the PET to
get 8K, and $280 more for the TRS-80 to get
16K. Both could probably be expanded with
user-installed memory chips for much less. Add-
itional RAM for both units goes in an expansion
box, not yet available. The TRS-80 comes with
4K of ROM, including BASIC, keyboard scanner,
cassette and video handlers, etc. It has provision
for a second 4K of ROM to get Level II BASIC,
and a third 4K ROM to get Level III. The PET
comes with 14K of ROM: 8K for BASIC, 4K
for the operating system, IK for a machine
language monitor, and IK for a diagnostic to
test all the hardware.

The PET video display is 25 lines of 40 charac-
ters, or 1000 characters total. An 8 x 8 dot
matrix is used for each character. The character
set is 64 ASCII, upper case only. In addition,
there are 64 graphics characters, including

various lines for limited vector graphics, the
playing card suit symbols, and others. Reverse
field video (black on white instead of white on
black) is available for all 128 characters by set-
ting the high order bit. The TRS-80 video dis-
play is 16 lines of 64 characters, or 1024 charac-
ters. 5x7 dot characters are used in a 6 x 12
dot matrix. The character set is also 64 ASCII
characters (upper case only), plus 64 graphics
characters. For each character position, any of
6 dots may be turned on, giving flexible point
graphics in a total field of 48 by 128 dots. The
high order bit of a 7 bit byte determines whether
a character or six dots is displayed. The PET
display is 9 inches (diagonal), integral to the
unit; the TRS-80 display is 12 inches, in a
separate video monitor.

The TRS-80 keyboard is a straight, 53-key
(Teletype) variety. The PET keyboard has 73
keys (53 in the center plus a 20 key numeric
pad), but the keys are arranged in rows and
columns, rather than offset like a typewriter.
The PET keyboard is crowded, and is probably
the worst feature of the unit.

The TRS-80 cassette interface operates at about
250 baud (25 cps); a 4K load would take about
160 seconds. It includes a motor on/off relay for
reading and writing data files. Only one cassette
recorder can be connected, making tape-to-tape
copying and editing very difficult. The cassette
recorder is a standard model sold by Radio
Shack, connected with cables to the computer.
The PET cassette interface operates at about
680 baud; a 4K load takes 60 seconds. One
cassette recorder is integral to the unit; it uses a
standard deck with special electronics. Another
cassette recorder, available as an option in a
month (the first option) for about $50, allows
tape-to-tape work. Both cassette recorders have
motor control.

Expansion from the "BASIC boxes" is planned
for both units. Radio Shack is expecting a $700
minifloppy and a $1,500 dot matrix printer by
the end of 1977, and later a serial I/O port and
an acoustic coupler. A non-standard 40 pin bus
connects peripherals (and the expansion mem-
ory) to the TRS-80. Commodore expects to
have their second cassette box out in a month,
a dot matrix printer in late 1977 or early 1978,
a minifloppy in early 1978, and some "fun

\

2: 17

1

peripheral" soon after. The PET comes with an
8 bit I/O port, plus an IEEE-488 interface bus
for peripherals. The IEEE-488 bus is used by
instrumentation manufacturers, is standardized,
and will probably be supported by some other
manufacturers. Motorola is working on a one-
chip controller for IEEE-488, since the interface
logic is pretty complicated.

The PET is I6V2 x 181/2 x 14 inches and weighs
44 pounds. The TRS-80 consists of a 161/2 x 8 x
3 box with the keyboard and electronics, a
16'/2 x 13'/2 X 12 video monitor, the cassette re-
corder, and a power supply (don't know the
total weight).

So far, the differences aren't outstanding. The
BASIC'S are very different, however. TRS-80
BASIC allows 26 numeric variables (floating
point only, 7 digit significance), 2 string variables
(A$ and B$, each with 16 characters maximum),
and one array, A(i). PET BASIC allows 676 each
of integer, floating point (10 significant digits),
and string variables; strings can have a maximum
length of 256 characters. PET arrays can have
multiple dimensions; also, trig functions are
included in PET BASIC but not TRS-80 BASIC.
The PET BASIC also has a real time clock. TRS-
80 BASIC includes commands to set and clear
points on the graphic display. Also, more ad-
vanced BASIC on the TRS-80 will become
available with two additional 4K ROM's. Both
BASIC'S include machine language functions,
PEEK and POKE, and the ability to read and
write data files with the cEissette recorder.
Neither includes the PRINT USING statement,
although both have other line format control
functions.

Both the PET and the TRS-80 are in production,
and have been shipped to customers. There is a
long line for both, however. I'm not sure about
the TRS-80, but the PET has a 90 to 120 day
waiting period, when ordered direct from the
factory. The only currently authorized dealer

for the PET is Mr. Calculator, a chain in Cali-
fornia (I haven't found one up here); however,
as soon as the back order situation improves,
computer stores and large chains will be carrying
it. The TRS-80, of course, is available at Radio
Shack, and later at Tandy Computer stores
(which will also carry the Processor Technology
SOL-20, the Apple-II, and other brands). One
other thing: manuals for the PET will be
available separately, this fall, and I hope to
order some of those if you're interested.

For more information, try "A PET for Every
Home", Sept. Kilobaud, and "The Radio Shack
TRS-80 Microcomputer System", Sept. Interface
Age. Also, there's "Radio Shack's $600 Home
Computer", Sept-Oct Creative Computing,
"Birth of the PET Computer", Sept-Oct Per-
sonal Computing, and "Radio Shack's New
Computer System", Oct Radio Electronics.

Several other new personal computers, in the
PET/TRS-80 price range, are coming soon.
Texas Instruments looks like the first giant
corporation to jump into the ring; their new
product announcement is expected this fall.
Bally (an arcade game manufacturer) has a mail
order unit available through JS&A. It's a com-
bination video game and computer, with 12K
of RAM/ROM, and a 160 by 100 dot video
interface that connects to your TV (no CEissette
or keyboard) for $300. Atari (another video
games manufacturer), and a European and
Japenese company are also expected to enter the
competition. National Semiconductor and
Hewlett-Packard have the capability to produce
personal computers, but I haven't heard any
rumors from them yet. IBM is a rather distant
possibility, I suppose. Zilog is announcing the
Z-800 this fall, which is also a factor.

NOTE: This material was originally printed in
"Northwest Computer Club News", October
1977 and is reprinted with the permission of
the author.

Editor's Notes: One additional difference that may be important to some users
is the fact that the PET Monitor supports assembly level code while the TRS-80
only supports BASIC. This means that you can write special routines in 6502
code on the PET. These may be called by the PET BASIC. This facility can
greatly enhance the power of the computer. For a user's view of the PET, see
"Meet the PET" by Charles Floto, MICRO #2, page 9.

\

2: 18

^w

Ludwig von Apple II

Marc Schwartz

220 Everit Street

New Haven, CT 06511

Owners of the Apple II know from the demon-
stration tapes that the Apple can make sounds.
Not all know that it can make music. Having
prepared a horse racing program, I decided that
it would be fitting to start out the game with the
bugle call heard at the track. The following pro-
gram does just that!

A few words of explanation are in order. The
series of "pokes" in lines 30 to 240 set up a
musical tone subroutine that is called in line 460.

Each note is represented by a four digit code in
A$. The first three digits of the code determine
the note, and the last digit determines the length
of the note. Line 410 decodes the first three
digits by converting each digit to ASCII (Apple
ASCII), subtracting 176 from each to give
three numbers, from zero to nine, and then
multiplying the first number by the second and
adding the third. This is one of many possible
ways of generating all the numbers from zero to
a large number (ninety in this case) using single
digits.

Line 420 takes the number just generated and
subtracts it from forty. This is done because the
subroutine as written is a bit confusing if you
want to make music, since the tones go up as the
numbers go down. This step corrects for that.

Line 440 determines how long each tone will
be. AS "ASC(A$(Z + 3) - 176)" increases, the
note lengthens: a "1" produces a very short
note, and a "6" makes a very long note. For
some reason, higher tones come out more
brief than lower tones.

Line 450 determines the tempo. A larger num-
ber speeds up the tune; a smaller one slows it
down. Tempo numbers can go from 1 to 255.

When the program reaches line 470, it returns to
line 400 to begin decoding the next four digits
and playing the next note.

I don't think that Chopin would need to worry
about competition from anyone using this pro-
gram, but it is fun to have a musical computer.

THE APPLE II BUGLE CALL

WITH THE APPLE II

10

REM MAKING MUSIC

20

DIM A$(255)

30

POKE

2,173

40

POKE

3,48

50

POKE

4,192

60

POKE

5,165

70

POKE

6,0

80

POKE

7,32

90

POKE

8,168

100

POKE

9,252

110

POKE

10,165

120

POKE

11,1

130

POKE

12,208

140

POKE

13,4

150

POKE

14,198

160

POKE

15,24

170

POKE

16,240

180

POKE

17,5

190

POKE

18,198

200

POKE

19,1

210

POKE

20,76

220

POKE

21,2

230

POKE

22,0

240

POKE

23,96

300 A$="001 10071521 1720172017201"

310 A$(25)="521 1521 1521 10071521 100710012"

400 FOR Z=1 TO LEN(A$)-3 STEP 4

410 Z1 = (ASC(A$(Z))-176)«(ASC(A$(Z-h1))-176)

-►ASC(A$(Z-h2))-176
420 Z2=40-Z1
430 POKE 0,Z2

440 POKE 24,ASC(A$(Z-h3))-176
450 POKE 1,75
460 CALL 2
470 NEXT Z
480 END

2: 19

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Till

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SN74aiM 16 SN745H 7S

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SH74170N
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CO400D

CM001

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CO4006
CD4007
CD40O9
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C04011
CCM0I2
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MC4044

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LM301H 35

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LK32DT-24 1.75

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LU340T-24 1 75

LM3S0N in

LM351CN SS

LINEAR

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LU377N

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HMU11
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WRITE and READ
EPROM

1702A unA ZTflfl
' PluRS Dirprlly into your ALTAIR/IMSAI Cnmpulf r

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Sorkrt llnil

The RPROM Snckr-I Unit is ronnected to the Com-
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• PrnRramminR is iiccomplishpd hy the Compuler

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Discounts available at OEM quantities. Add $1.25
for shipping. California residents add 6% sales tax.

CATALOG FREE WITH $10.00 ORDER

MICROBES

Tiny Bugs in Previous MICRO

1:13 HYPERTAPE and ULTRATAPE

00E9 3700 Hz Pulse Duration = in
OOEB 2400 Hz Pulse Duration = I£

1:19 COMPUTER CONTROLLED RELAYS

Error in the Circuit Diagram. A
single 7404 inverter may not have
enough drive for two relays. Remove
connection between Pin 2 of Write
Mic Relay and Pin 2 of Write Remote
Relay. Connect 7404 Pin 9 to 7404
Pin 11 and connect 7404 Pin 10 to
Write Mic Relay Pin 2. Add a diode
between Pin 2 and Pin 1 of the Write
Mic Relay. Each relay is now driven
by an independent 7404 inverter.

2:22

i[£a3(3^(«)i

We have the KEM
KIM-1 Expansion Module
the easy way to expand your KIM-1

* Generates S-100 Bus

* Accepts 2708 EPROMs

* ASCn Keyboard port

* Mates the MVM-1024 Video Module

Write for complete info on the
KEM and MVM-1024 Video Module

A Riverside

rxr

ELECTRONIC DESIGN INC.

1700 NIAGARA STREET
BUFFALO, NEW YORK 14L'07

FANCY DATA TERMINAL Build this terminal using a CPU-1 a VDB-1

an ASCII keyboard, a TV set or monitor,
power supply etc. and a 2704 EPROM, pro-
grammed to handle scrolling, data input,
output, etc.

FDT-1 documentation includes EPROM pro-
gram listing, construction and operating
hints. Doc. only $5. ppd, Pre-programmed
EPROM available.

SS50 BUS PRODUCTS---BUILD YOUR 6502 AROUND A POPULAR BUS STRUCTURE

CPU-1 A CENTRAL PROCESSOR using the MOS TECHNOLOGY 6502 & 6530-004 TIM
MONITOR ROM, Can use crystal or RC clock (on board). Has current-loop or RS232
I/O lines plus 8 general purpose I/O lines and 2 handshake lines. Board has provisions
for a 2704/8 or 2716 for program or subroutine storage. EPROM can control startup
from reset if desired. Use with SWTPC or equiv. memory or VDB-1 to form a com-
plete system. SS50 Bus compatible. Bare board and documentation $29. Doc, only $5,

VDB-1 A 32 character x 16 line video display generator. 2 pages of display possible.
Provisions for RF modvilator. On board memory, regulation, optional inverters. See
Nov. '76 BYTE article by A.I. Anderson for circuit description. Plugs into SWTPC or
equiv. SS50 Bus. Bare board and documentation $29, 00. Documentation only $5,00

SPECIAL CPU-1 & Doc. , VDB-1 & Doc. , FDT-1 Doc. ALL FOR $55. 00

Add $2. 50 Per Order S/H. Ohio residents add 4%. Doc. price refundable with order.

F&D ASSOCIATES, Box 183, New Plymouth, Ohio 45654

^

The Challenge of the OSI Challenger

Joel Henkel

Old County Road

Hillsborough, NH 03244

One of the factors that a purchaser of a micro-
computer system must consider is the degree of
"do it yourself" hardware and software effort he
will have to exert to get his system doing what
he wants. This effort, not evident from manu-
facturers' literature, can be critical for user
satisfaction, as became evident in our experience
with the OSI Challenger. These notes evaluating
the Challenger may be helpful to prospective
purchasers.

In any hobby industry, user skills are assumed.
This is emphasized for microcomputer firms that
formerly catered to electronic kit builders. OSI
is one of these, having supplied special PC board
kits to hams. They follow their own packaging
philosophy that differs from the "standard"
S-100 bus configuration. Their brochure ex-
plains that the 100 pin S-100 connectors were
rejected because the fingers were subject to poor
contact. Instead, OSI uses MOLEX connectors,
which make positive contact. The brochure goes
on to describe the rejection of on-board voltage
regulators in favor of a self contained regulated
power supply.

OSI circuit boards are larger than standard S-100
bus boards. This accommodates their design
philosophy of packing many optional functions
into one foil pattern. For example, their 430B I/O
board supports: an eight channel multiplexed
eight bit analog to digital converter, two chan-
nels of eight bit digital to analog conversion and
a UART controlled cassette I/O interface or an
RS232/twenty mil loop I/O interface.

Our system came without keyboard or video
monitor. Interfacing for these is left to the user.
The computer cabinet has two holes in its rear
panel for user implemented I/O cabling from
individual boards. The keyboard DIP socket and
video output RCA connector are available at the
edge of the 440 video board. MOLEX connectors
on the edge of the 430 board provides access to
the various I/O options.

Hardware documentation consists of kit con-
struction manuals for individual boards, even if
the boards are purchased assembled. Various
options are treated separately. Overall hardware
system documentation is completely lacking.

For example, nowhere is there a description of
the bus convention and pinout. One must gen-
erate these from actual inspection of board foil
patterns. This exercise reveals interesting peculi-
arities, such as bringing the NMI (non-maskable
interrupt line) and IRQ (interrupt request line)
onto many boards and leaving them unconnected.

The software is sophisticated. One enters the
system by resetting. A prompter, D/M, comes up
on the video screen. To enter the video monitor,
styled after the KIM, enter M and the six hex
digits appear near the top of the screen. For
DOS (disc operating system), enter D and the
DOS is brought up through BASIC by a boot-
strap ROM. (Earlier versions required loading a
short sequence of memory locations using the
video monitor.) From BASIC one can enter the
DOS, from which it is possible to go to various
modules, such as an extended monitor, back to
BASIC, or to activate a few DOS commands,
such as loading and recalling disc files, executing
programs, or switching floppy disc drives (for
dual floppy discs). The EXTENDED BASIC by
MICROSOFT has many advanced features, such
as string functions, and is apparently much
faster than a comparable 8080 BASIC.

Software documentation is poorly organized.
Perhaps with so many possible options, the job
of creating well organized system documenta-
tion was beyond OSI 's capability. Our experience
with software documentation availability was
sobering. The system comes with all OSI soft-
ware on discette. However, only a BASIC users
manual is included, beyond a general system
description. One has to order software user
manuals separately. We waited a long five
months after order for ours.

We have used two versions of the DOS, an ori-
ginal 1.1 version and an updated 2.0 version.
One interesting change has to do with copying
the DOS itself. The original version could not be
copied and an explicit notice to that effect was
included. An unfortunate set of circumstances
could come about, however, that would wipe
out track one, completely disabling any further
loads of the DOS. If computer power fails (or
one turns off the computer) with the disc in its
drive, out goes track one! Apparently a number

\

2:23

,^^(3[^(£)j

of users had this happen (including us). Version
2.0 has complete copying capability. According
to instructions the first thing one should do is
copy the DOS and store away one copy in case
of wipeout.

Another change from the original version is the
serial display output rate to the video monitor,
which was increased from ten characters per
second to several times that rate. A third change
in the DOS is an augmented facility to read and
write disc files.

The 440 board video display format chosen is
twenty four characters per line, which is too
small. One can only speculate on the reason for
the short line.

Many applications could readily use a real time
operating system, (RTOS). OSI does not offer a

RTOS, but has advertised that one, modelled on
DEC'S RTSll is in the works. When contacted
recently, however, OSI reported that it has in-
definitely postponed development of its RTOS
in favor of development of a business system.
The contemplated RTOS may explain the inter-
rupt lines found in the foil patterns of several
boards mentioned earlier, and a foU pattern
option on the 470 floppy disc controller board,
a real time clock in the form of a divider chain
driven by the on-board crystal clock.

In summary, the OSI Challenger offers a lot of
computer for the money. The tradeoff is the
board orientation rather than system orienta-
tion, requiring a larger than average effort on
the part of the user to bring his system up. This
effort includes I/O interface cabling and "reading
between the lines" in the supporting documenta-
tion.

^

2:24

il^3(S^(£)i

cyVLicro -Computer
R^epairs !

all nQakes^alLnoocDeLs
ReasonaBle Rates

open noon-loprri
man. - sat.

the COnPUTEK DOCTOK/mc

'12 MOWAKD STo, CAM5KIDQE~MA55.,02139

[617] 661 -<5 792

^

Improving KIM-1 Keyboard Reliability

KIM Application Note

MOS Technology
950 Rittenhouse Road
Norristown, PA 19401

The keyboard on some KIM-1 's has a "bouncy"
key problem and the "9," "D," or "C" keys
may fail entirely. The problem is due to the use
of the outer edge of the snap-action discs to
jump over the center contact line on the key-
board pc. Since the discs are only held against
the pc board with tape, the contact is poor.
There are five of these jump-overs in series for
the "C" key (four for the "9" key), thereby
compounding the problem. To check for the
problem, measure the resistance from keyboard
pin 3 to pin 1 5 (numbered from left to right as
shown) with the "C" key depressed. It should
be less than about 10 ohms.

Fortunately, this problem can be easily correct-
ed. The solution is to solder a thin wire jumper
across these poor contacts as follows. Disassemble
the keyboard by first removing the four screws
on the back of the keyboard at the comers.
Then remove the two remaining screws that hold
the keyboard to the KIM-1 (note for reassembly
that they are longer), being careful not to pull
the keyboard pc board away from the KIM-1
board - it's only attached by the solder at one
end. With the KIM-1 upside down, separate the
black keyboard panel from the keyboard pc
board. You may wish to cover the keyboard
with masking tape to hold the keys in place.
After cutting four small holes through the clear
Mylar at the locations indicated by an X in the
figure, the lines from "C" to "9," "D" to "9,"

"A" to "7" and the line to "B" are exposed.
Connecting these points by soldering a thin
wire between them routed as shown is suffi-
cient to bridge the five potentially poor con-
tacts.

— r— T — r-

9 O O t

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2:25

l^3(S^(l)i

MICRO is published bi-monthly, six issues per year. Subscriptions $6.00 (USA).
Subscription starts with next issue. Back issues are $1.50 each (Nos. 1 & 2]

Rv

NAME:

ADDR:

CITY: STATE:

ZIP:

[] Please include my name and address in mailing lists that you make available
to dealers, suppliers, and other legitimate 6502 interests so that I may be
kept informed of new products, current developments, and so forth.

[ ] Please DO NOT include my neime and address in mailing lists that are made
available to outside sources.

^

Send your check to: MICRO, P.O. Box 3, S Chelmsford, MA 01824

i^3(3^(>)i

COMPUTER
SHOP

288 NORFOLK ST. CAMBRIDGE, MASS. 02139
corner of Hampshire & Norfolk St. 617-661-2670

r

MEMORY

4 K MEMORY BOARDS THAT CAN BE USED FOR YOUR KIM

The VF8 4K memory boards have dual 22 pin .156 pinouts
but with different pin assignments than your KIM. Instruc-
tions for jumpering between connectors are included.
This board has been used as modified bv many KIM owners
FULLY ASSEMBLED AND TESTED REG. PWR. $129.00 '

LOW POWER RAM ADD............ $ 10.00

KIT .....$ 74.50

jm, w^mmi^ full set sockets for kit j% lo.oo

W 5P VF8 MOTHERBOARD-BUFFERED FOR 4 BDS. $ 65.00
CONNECTOR ASSEMBLY- KIM TO VF8 $ 20.00

CS lOOVIDEO TERMINAL BOARD FOR YOUR KIM

The CSlOO VIDEO TERMINAL BOARD IS A 16 LINE ^^iiajii".

BY 64 CHARACTER DISPLAY GENERATOR WITH SHȤ^

CURSOR CONTROL AND EDITING Connect a 5V. ^ra^&=^

ASCII Keyboard to it, a Regulated 5 Volt, Unregulat-
8 Volts, or 8 Volts AC, and your KIM Teletypep ort
to it along with a video monitor and away you go with
all the convenience of a Video Terminal on your KIM.

The CSlDO-KIM is a fully enclosed portable cabinet
that has cutouts for the KIM keyboard and hex dis-
play. Space is provided for your cassette recorder
ASCII Keyboard, power supply, and extra memory
boards. The display shown was generated by our
Video Terminal Board connected to the KIM.
The cabinet is heavy duty l/,e inch aluminum fin-
ished in a blue spatter with white panels. An S]DO
low profile e 3 slot motherboard is available that
fits under the KIM is available

CSlOO Cabinet cut out for KIM $ 129. 00( )

3 Connector SlDO MB Assem. $ 75.00( )

VF8 4K Memory Board Assm. S 129. 00( )

V.F8 4K Ram Kit $ 74.50( )

Low Power 21D2 Option S 10.00( )

Socket Option......... .......$ 10.00( )

.......... V.F8 Motherboard $ 65.00(

Connector Board......... S 20.00(

CSIDO TIM Kit S 129. 95(

■•••••..•. CSlOO 6502 CPU Kit. ..........$ 169. 95(

CSlOO Front Panel Kit......... $ 129. 95(

CS1D0-VT3 Vid. Term. Bd.KitS 155.00(

••••••"•• CSIDO-VTB Vid. Term. Bd.Asr$ 185.00(

KIM-l-i;. -5 245.0D(

........ Total of Order ...........$.....

Mass. Res. Sales Tax...... .....$....

Shipg. 1% (S2.00 minimum)... ..$

Total Remittance or Charge.. ..$ ^

BAC,VISA,MC NO.

SIGNATURE........

NAME......

ADDRESS............

CITY....

• STATE... ...... ZIP....

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OOEF
OOFO
OOFl
00F2
00F3
OOFii
OOFS
0OF6
00 F7
00F8
00 F9
OOFA
00 FB
OOFC
00 FD
00 FE
OOFF

Label

FCL

PCH

F (PREG)

SP (SPUSEft)

A {AGO

Y

X

CHKHI

CHKSUM

INL

INH

POINTL

POtNTH

TEMP

TMPX

CHAR

MODE

Important Addresses of KlM-1 and Monitor

William R- Dial

438 Roalyn Avenue

Akron, OH 4^320

FUTlCtlCUl

PrograiB Coumtei: - Lo Byte

Program Counter - Hi Byte

Status Register of Processor

Stack Polluter

Accumulator

Y-Begister

X-Reglster

CheckeuH! on Tape, Bi

Checksum on Tape, Lo

Input Buffer t Lo - Display Buffer

Input Buffet, Hi - Display Buffer

Pointer, Lo - Display

Pointer, Hi - Display

Temporary Storage Byte

Teinporary Storage Byte

Current Character for TTY

Byte Indicating KYBD or ITY Mode on KIM

Set "00" for Binary

Detail of Processor Status Register P (OOFl)

ait No. 2 1 5

K V

4

3 2

1

B

3 I

Z

C
1

Fla^s (1 « set)
-Carry

. Zero Result

Interrupt Disable

-Deciioal Mode

Break Coicmand
Reserved for Expansion
Overflow
Negative Result

OlFF
OlFE
01F8 etc.

• ■ ■ ■ r

STACK

Needed to Process Interrupts, save Addresses, etCi

2:27

J

I/O Forts, Interval Timers, and 6530 RAM Usage

Function

Address

Label

1700

PAD

1701

PADD

1702

PSD

1703

PBDD

1704 / 1744 CLKIT

1705 1745 CLKBT

1706 1746 CLK64T

1707 1747 CLK1024T
1707 1747 CLKRDI
1706 1746 CLKEDT

170C
170D
170E
170F

1740

1741
1742
1743

1780

17E7

i7Ee

17E9
17EA
17EB
17EC
17F2
17F3
17F4
17F5
17F6
17F7
17F8
17F9

174C IT

174D 8T

174E 64T

174F 1024T

SAD

PABD (SADD)

SBD

PBDD (SBDD)

CHKL
CHKH
SAVX

VEB

CNTL 30

CKTH 30

TIMU

SAL

SAH

EAL

EAH

ID

Output)
Input)

Port A Data (user 1/0)
Port A Data Direction {1
Port B Data (User 1/0)
Port B Data Direction (0

INTERVAL TIMER

17D4 et seq User

1744 et seq KIM MONITOR

Read Tlsie Out Bit
Read Time

TIMES USED vhen IRQ Interrupt at PB7 needed

i

Port A Data
Part A Data
Port B Data
Port B Data

(KIM ICKITOR)
Blrectlon
(KIM mNlTOR)
Directian

Available iteiHory Block (Prograsi PLEASE ^ etc.)
Checksum for Tape Monitor
Storage Location

rt

Volatile Execution Block
TTY Delay
TTY Delay

Starting Address - Lo (Audio and Paper Tape)

- HI
Ending Address • Lo

- Hi

ID Number (Program No. on Tape)

17FA/FFFA NMIV (NMII) Stop Vector (Stop = ICOO) Load 00

FB/FFFB (NMIH) IC

FC/FFFC RSTV (ESTL) RST Vector 00

FD/FFFD (ESTH) IC

FE/FFFE IRQV (IRQL) IRQ Vector (BJOC = I<X)0) 00

FF/FFFF (IRQH) IC

2:28

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SUB-ROUTIHES - 6530-003
Label

Addresa

1800

1873

1932

194C

195E

196F

197A

199E

19C4

19KA

19F3

lAOO

1A24

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HEXOUT

OUTCHT

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ZRO

INCVEB

ItDBYT

PACKT

RLGHT

BDBIT

PLLCAl

SUB-ROUTINES

- 6530-002

ICOO

SAVE

1C22

RST

1C2A

DETCPS

1C4F

STAKT

ICDC

PCCMD

1C64

CLEAR

1C6A

READ

1C77

TTYKB

FurtctlQD

Diaap Memory to Tape

Load Memory from Tape

Initiate Volatile Execution Block

CoBipute CHKSUM for Tape Load

Output One Byte

Convert LSD of A to ASCII and Output to Tape

Output to Tape One ASCII CHAR (Use Subs ONE & ZRO)

Output to Tape = 1 (9 pulses 138 ^ sec each)

Output to Tape (6 pulses 207 ^ sec each)

Sub to INC VEB + 1, 2

Sub to read Byte from Tape

Pack A = ASCII into SAVX as Hex Data

Get 1 Character froia Tape and Return with
Character in A (Use SAVX + 1 to ASM Oisr)

Gets one bit from Tape and returns It in
sign of A

Diagnostics ; PLL calibrate Output, 166^ sec
pulse string

KIM Entry vis STOP (NMl) or BRK (IRQ)
Also SST

KIM Entry via RST (Reset)

Count Start Bit

Make TTY/KB Selection

Display Progrem Counter by Moving PC to POIHT

Clear Input Buffer INL, IKH

Get Character

Main Routine for Keyboard and Display

2:29

Address

1ED4

lEEB

lEFE

1F19
IFIF

iFAe
ir63

1F6A

1F91
1F9D

IFAC
1FD5

1FE.7

Label

1CE7

LOAD

1D42

hmp

lElE

PRTPNT

1E2F

CRLF

1E3B

PRTBYT

1E5A

GEICH

1E88

INITS

1E9E

OUTSF

DELAY

DEHALF

AK

SCAND

SCAJTDS (DISPLA)

CONVD

IMCPT

GETKEY

CHK
GETBYT

PACK

TOP

TABLE

^

Function

Load Paper Tape from TTY

Duimp to TTY from Open Cell Address to LIMHL,
LlbGlH Limit: High , H and L

Sub to Print FOINIL, POINTH

Print String of ASCII Chsractets from
TOP + X CO TOP

Priot 1 Hex Byte as Two ASCII Qiaracters

Get I Character from TTY, Return from Sub with
Char In A. X ie preserved and Y returned = FF,

Initialization for SIGMA

Print One Character CHAR = A.
X is preserved, Y returned = P7.
OUTSP Prints One Space .

This loop simulates DETCPS Section and will
delay 1 Bit Time.

Delay half Bit Tine - Double right shift of
Delay Constant for a Div by 2.

Sub to Determine if Key is depr«a.sed or

Condition of SSW

{Key not dep or TTY Mode A = 0)
(Key dep or KB Mode A = not aero)

Output to 7 Segment Display

Lights 7 Segment Display

Convert and Display Hex - Used hy ECAOT only

Sub to Increment POINT

Get Key from Keyboard, Return with A = Key
value. If A GT. than 15 then Illegal or no Key,

Sub to Compute Check Sum

Get 2 Hex Characters and Pack Into INL, INH.
X preserved, Y returned = 0,

Shift Character In A into IWL, INH

Table

Table Hex to 7 Segment

2:30

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